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Factory cruise control with different engine?


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#1 bthotrod

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Posted 25 November 2017 - 05:37 PM

I honestly have no idea how the factory cruise control works other than it has vacuum ran to it and some wires plugged in.

If anyone could give me a basic run down of the inputs it needs to work/ any ideas on the possibility of making it work with a 302 swap, I'd greatly appreciate it!! Just throwing it out here, you all know more than I do!





#2 Zoggy87

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Posted 25 November 2017 - 10:34 PM

It's tied into the vacuum lines and has a valve with pump for when in boost. But it's controlled by the computer if I'm not mistaken. Not sure how easy it would be to utilize. They make aftermarket cruise units if not.

#3 bthotrod

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Posted 26 November 2017 - 06:42 PM

View PostZoggy87, on 25 November 2017 - 10:34 PM, said:

But it's controlled by the computer if I'm not mistaken... They make aftermarket cruise units if not.

Trying to avoid an aftermarket cruise system if possible, it'd be nice to figure out how to make what I already have work. And I've heard its ran under a separate computer than the ECU somewhere on this forum (the same computer as the heater controls and such I believe.)

#4 Laodicea

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Posted 24 January 2018 - 12:46 PM

It works fine on my 2jz....it is totally separate from ecu.
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#5 techboy

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Posted 24 January 2018 - 02:48 PM

Vacuum wise you'll just have to run a vacuum line to it, most likely the same there now as long as your retaining the same HVAC setup in the car.  Electrically you'll have to look at the FSM and figure what the various wires do, I think it's only a 3 or 4 pin connector, and then wire accordingly.  I'm assuming with the swap you won't be using the factory wiring harness, so you'll have to splice it in.
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#6 slowquest

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Posted 25 January 2018 - 10:50 AM

The cruise control is completely standalone from the engine other than the cable on the throttle body.  It reads speed from the reed switch in the speedo head and maintains it by pulling more or less throttle.

#7 bthotrod

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Posted 25 January 2018 - 07:07 PM

This is all good news! Thanks so much guys! And since I'm running a carb setup, if I use the same throttle cable as the original 4cyl on my carb linkage will it be able to move throttle with that? I'd assume it would

#8 slowquest

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Posted 25 January 2018 - 07:13 PM

Yes it will.  The cruise is connected at the gas pedal, not the throttle body as I stated earlier.  You will need a good vacuum source, either a nonturbo engine, or a vacuum pump (which these have stock, but some don't work)

#9 bthotrod

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Posted 29 January 2018 - 08:16 PM

View Postslowquest, on 25 January 2018 - 07:13 PM, said:

Yes it will.  The cruise is connected at the gas pedal, not the throttle body as I stated earlier.  You will need a good vacuum source, either a nonturbo engine, or a vacuum pump (which these have stock, but some don't work)

Yay!!! Actually really excited about this, I'm building the car to also be able to make a pretty hefty trip when I come down from college and without cruise that trip would be a pain. Appreciate all the info! And yeah, the V8 should make pretty good vacuum and I'll add in a small vaccum canister before the cruise just for a little more help.

#10 mikec

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Posted 24 March 2018 - 10:35 PM

Compared to current car designs where the main computer handles engine, timing, transmission, cruise control, OBD-II diagnostics, traction control, etc.the StarQuest cruise control is simple and is a completely "add-on" device.  As was already mentioned, the primary speed input comes from a magnetic reed switch attached to the back of the speedometer, a ring-shaped magnet (with 4 magnetic poles) pulses this switch in sync with engine speed.  The cruise control computer uses the engine vacuum powered actuator to tug on a cable that's attached to the top of the throttle pedal linkage under the dash.  Switches on the brake and clutch pedal CANCEL the cruise control when either pedal is pressed.

The system is very simple and has pretty much no knowledge of the engine.  As long as the pedal-to-vehicle-speed of your engine swap doesn't change drastically it should still work after the engine swap.  I installed a junkyard Conquest cruise control unit into my '78 Corolla for example - a small 1.6liter carburetor engine and it worked on the first try.  StarQuests use a fairly generic Nippondenso speedometer mechanism that looked a lot like the one on my Corolla - so much so that the small reed switch and the metal bracket it's attached to bolted to existing threaded screw holes on my Corolla!  No adapting needed.

Cruise control systems used to be powered by engine vacuum - that was a safety consideration.  If the cruise control went stupid and "floored it" the engine vacuum would go to low levels and the cruise actuator would thus not have any power to pull on the throttle cable and it'd relax the throttle... until vacuum built up again.  You'd get a surging characteristic that'd pretty much wake up any driver and would keep the car from rapidly increasing speed.  StarQuests though, with turbo boost pressure replacing engine vacuum quite often, can't take advantage of this.  Ergo the vacuum pump mounted between the headlights.  A small pressure switch detects when intake manifold vacuum is low - or when boost is present - and triggers a relay.  That relay then powers the vacuum pump to supply vacuum to the cruise control actuator.  One-way check valves (those white plastic things in the vac hoses by the wiper motor) isolate boost pressure from the cruise circuit and isolates the vacuum pump from everything else.  The small black metal tank by the ABS actuator is a vacuum reservoir for the dash vent actuators; that's a separate circuit from the vacuum pump and cruise control vacuum circuit.  If your engine swap is a non-turbo/non-supercharged setup, you might not even need the vacuum pump and its relay.  But preserve the vacuum tank and those check valves so your dash vents to switch modes every time you mash the gas pedal!

It's a common misconception that the vacuum pump also helps with the dash vent actuators... nope.  The vacuum pump is only turned ON when the cruise control main switch is ON and when that vacuum sensor triggers the relay.  If the main cruise control switch is OFF, the vacuum pump can't run.  That's why the dash vents have their own reservoir to maintain the vents during boost operation.  You don't really want to tie the dash vents and cruise together either - i.e. don't share the reservoir, don't share the vacuum pump - because the cruise control actuator works by venting vacuum.  It becomes a vacuum leak that would cause your dash vent actuators to act stupid.

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#11 bthotrod

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Posted 25 March 2018 - 12:29 AM

Thanks Mike! That's a LOT of useful information that I didn't know, I really appreciate it.

As far as detecting actual speed, this is done on the speedometer in the dash right? Not the weird adapter looking piece that the trans side of the cable goes into? The car came with no transmission, but the speedometer cable had this metal adapter thing on it that had an electrical plug and wires coming from it. Sorry for my ignorance, but I read somewhere it might be ABS - I have no idea. (ABS is removed though, so if it is ABS I'm not worried about it.)

#12 mikec

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Posted 25 March 2018 - 02:43 AM

Yes, cruise control detects vehicle speed from the speedometer reed switch.  That gizmo attached to the side of the transmission is a "pulse generator" and is in fact the speed sensor for the ABS.  The ABS, like the cruise control, is an independent add-on system on StarQuests.

There are several duplicated sensors on StarQuests due to the added-on history of the vehicle.  There are several engine coolant temp sensors for example...  each driving a separate stand-alone system/function.  Again, on more modern cars all of this electronic/mechanical stuff would be more integrated.  That integration though means it is harder to tweak/change/modify anything too.  And if one part fails a whole lotta stuff on modern cars dies at once.

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#13 bthotrod

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Posted 25 March 2018 - 03:38 PM

Awesome! I appreciate the shared knowledge!! YAY for cruise control!




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